Process for producing difructose dianhydride iii crystals

ABSTRACT

A process for producing the crystals of difructose dianhydride III (DFA III), namely a indigestible disaccharide where two fructose molecules are bonded to each other at positions 1,2′ and 2,3′ (di-D-fructofuranose-1,2′:2,3′-dianhydride), where solutions containing DFA III are adjusted to and/or maintained at pH 5 or more, preferably pH 5 to 8, and more preferably 6 to 8. DFA III can be produced industrially without lowering the crystal yield even when the crystallization thereof is done in a recycling system; additionally by adjusting the total fructose content in mother solutions for (crude) crystallization to 5% or less per a solid content basis and adjusting the fructose content to 1% or less, DFA III can more effectively be produced.

TECHNICAL FIELD

The present invention relates to a process for efficiently producing thecrystals of difructose dianhydride III (sometimes referred to as DFA IIIhereinafter). In a recycling system for producing DFA III, in accordancewith the invention, the crystal yield is never lowered. Therefore, theprocess of the invention is very excellent as an industrial process forproducing DFA III.

BACKGROUND OF THE INVENTION

DFA III is a functional oligosaccharide with an effect on promoting theabsorption of minerals primarily including calcium, a diuretic effect,and an effect of ameliorating constipation. DFA III is a cyclicdisaccharide (di-D-fructofuranose-2′,1:2,3′-dianhydride), where thereducing end of each of two fructose molecules is bonded to a hydroxylgroup at a position other than the reducing end of the other fructosemolecule. DFA III is highly soluble in water at a solubility of 90 to95% of the water solubility of sucrose, while the sweetness level isabout 52% of that of sucrose. Additionally, DFA III is a substancehighly resistant against heat and acids.

As one process for producing DFA III, a process for producing DFA IIIhas been proposed, comprising interacting a bacterium of the speciesArthrobacter ureafaciens or an enzyme generated by the species withinulin and/or an inulin-containing plant extract to prepare a solutioncontaining DFA III, passing the solution containing DFA III through acolumn packed with active charcoal to allow DFA III to be adsorbed onthe active charcoal, subsequently eluting the column with ethanol torecover a fraction at a high DFA III content and evaporating and dryingthe fraction (see for example Patent Reference 1).

Another process for producing DFA III has also been proposed, comprisingpassing inulin and/or an inulin-containing plant extract through acolumn packed with inulin fructotransferase immobilized on animmobilizing material, to generate a DFA III-containing solution, andsubjecting the DFA III-containing solution to a purification step forexample with anion exchange resin or active charcoal to generate a DFAIII-containing syrup or an evaporated and dried product (see for examplePatent Reference 2).

Furthermore, it is also described that the reaction of inulin withinulase II allows for the industrial production of DFA III at a highpurity (see for example Patent Reference 3).

However, absolutely not any of these references tells about the yield ofcrystallized DFA III. Not any report has been issued about an efficientindustrial production of the crystals of DFA III. Therefore, suchproduction has been totally unknown.

Patent Reference 1

-   JP-B-56-26400

Patent Reference 2

-   JP-A-1-285195

Patent Reference 3

-   JP-A-11-43438

Problems that the Invention is to Solve

Following the recent development of a useful application of DFA III,demands toward DFA III have been increasing. For medical use as well asfor dietary use, the crystals of DFA III at a high purity have beendesired, from which sugars except DFA III and other various impuritiesare removed. Desirably, a process for more efficiently producing thecrystals of DFA III from solutions containing DFA III and an industrialprocess for producing crystallized DFA III, in particular, may beestablished.

Means for Solving the Problems

In such technical circumstances, the invention has been achieved for thepurpose of developing a process for producing the crystals of DFA III,particularly an industrial process for efficiently producing thecrystals of DFA III.

Thus, the inventors developed a process for producing the crystals ofIDEA III as a product, comprising defecating and filtering a DFAIII-containing solution, subsequently concentrating the resultingfiltrate for crude crystallization to separate a crude crystal syrup,dissolving the crude crystals thus and defecating and filtering theresulting solution, concentrating the filtrate, crystallizing theconcentrate, and separating the crystal syrup. For efficient preparationand industrialization, furthermore, the inventors constituted arecycling system for recycling the crude crystal syrup and/or thecrystal syrup separated as described above to a crystallization step tocontinuously produce the crystals of DFA III. The inventors firstencountered a serious drawback such that the crystal yield of DFA IIIwas decreased over time, involving difficulty in producing any crystalsof DFA III, so that the industrial production thereof was substantiallynever achieved.

So as to overcome the serious drawback first found, the inventorsthoroughly investigated the cause of the decrease of the crystal yieldof DFA III from various aspects.

DFA III-containing solutions contain substances other than DFA III.These may be for example substances derived from chicory in extractinginulin from plants such as chicory, or substances synthesized ingenerating inulin from sugar via enzymatic synthetic preparation, orenzymatically degraded inulin-derived substances via the enzymaticreaction for producing DFA III from inulin. In the process for producingthe crystals of DFA III, DFA III-containing solutions are retained forsuch a long time and the solutions are exposed to such severe conditionsincluding high temperature during the concentration process of thesolutions for a long time that the composition of the DFA III-containingsolutions may be modified under these conditions, to generate new othersubstances. Various substances as described above may affect thecrystallization of IDEA III. Because the DFA III-containing solutionsare recycled at the purification and crystallization step of DFA III,new substances other than DFA III generated as described above maysometimes accumulate.

Inulin as one of raw materials for DFA III is a polysaccharide wherenumerous fructose molecules are connected in series to one glucosemolecule. When an enzyme with hydrolysis and transition activitiesreacts with inulin, DFA III is generated as the main component while asother by-products, fructooligosaccharides such as tetrasaccharide(G-F-F-F) and pentasaccharide (G-F-F-F-F) are generated. Thesetetrasaccharide and pentasaccharide are poorly resistant against heatand are therefore modified at a step at high temperature as in theconcentration step, to be decomposed into sugars of smaller molecularweights, finally into organic acids and the like. Consequently, the DFAIII-containing solutions are at a decreased pH. The inventors found thatthe decomposition thereof was further accelerated at the defecation andcrystallization steps of DFA III especially in the production process ina recycling system.

At the enzymatic reaction step of generating DFA III from inulin, thereaction proceeds under relatively mild temperature conditions such asaround 60° C. Although the initial enzymatic reaction was at a neutralpH range (pH 6-7), the reaction solution on the completion of thereaction was decreased to pH 4 or therearound. Thus, it was found thatthe DFA III solutions enzymatically synthesized by the enzymaticreaction process are generally at pH 5 or less and it became one of thefactors to cause the decomposition of tetrasaccharides andpentasaccharides, at a subsequent step leading to the DFA IIIcrystallization.

In progress to a crystallization step of DFA III, substances other thanDFA III are mostly derived from sugars, where monosaccharides glucoseand fructose, a disaccharide sucrose, trisaccharides, tetrasaccharidesand substances larger than (fructooligosaccharides), organic acids andthe like may exist in mixture. Additionally, DFA III is a substancehardly decomposed thermally or with acids, as described above.

In view of those described above, the inventors made investigations fromvarious aspects about diverse substances in DFA III-containing solutionswith an influence on producing the crystals of DFA III. Surprisingly,the inventors first found consequently that the pH of a solutioncontaining DFA III and sugars existing in admixture, particularlyfructose and sucrose, affected specifically the crystallization of DFAIII.

The inventors therefore made investigations about factors specificallyaffecting the crystallization of DFA III from various aspects, whichfactors were first found by the inventors.

With attention focused on the substances except DFA III, the inventorsmade various investigations. Consequently, the inventors found that thedecomposition of substances readily decomposable at a series of stepsfor crystallizing DFA III could be suppressed and the conversion of suchsubstances into other substances could be blocked at minimum, bymaintaining and/or adjusting all of the solutions containing DFA III atthe defecation, concentration and crystallization steps of DFA III to pH5 or more, preferably to pH 5 to 8, more preferably to pH 6 to 8 (by theglass electrode method). Additionally, the inventors newly found that bycrystallizing DFA III from a mother solution for the (crude)crystallization at pH 5 or more, preferably pH 6 to 8, the crystal yieldwas never lowered but was maintained or increased.

It has never been known that the crystal yields of sugars such as DFAIII and other sugars are modified by the pH of mother solutions for thecrystallization. Thus, the finding is a totally new finding.

As a method for maintaining and adjusting the pH of such solutions atthe individual steps in producing DFA III within the range describedabove, the solutions at the individual steps should effectively becontrolled at 70° C. or less as much as possible. Additionally, analkaline agent may be added to actively adjust the pH. The alkalineagent to be used includes for example sodium hydroxide (caustic soda),potassium hydroxide (caustic potassium) and sodium carbonate (limesoda). Additionally, the purity of DFA III in the solutions at the stepscan be increased and the pH decrease can be prevented, concurrently, bysimultaneously removing acidic substance such as organic acids andsugars except DFA III in the solutions at the steps by using achromatographic method.

As a method other than the method described above, a DFA III-containingsolution containing also acidic substances is passed through anionexchange resins to adsorb the acidic substances via ion exchange toremove the acidic substances.

The inventors newly found that fructose and sucrose contained in amother solution containing DFA III for the crystallization were factorscausing the inhibition of the crystallization of DFA III. It was foundthat the fructose content at 5% or less, preferably 1% or less on asolid content basis in a mother solution for the crystallizationenhanced the crystal yield of DFA III during the crystallizationthereof.

Under the condition that the pH value of a mother solution forcrystallization of DFA III was 5 to 7 and the supersaturation degree(referred to as supersaturation degree “S” in accordance with theinvention) of DFA III concentration in the mother solution to thesolubility of DFA III at a temperature on the completion of thecrystallization was 4.4 or more, the flowability of the massecuite wasso significantly reduced in the mother solution containing DFA III atany purity for the crystallization, so that it was found that thepurging involved was much difficulty. Under a condition that thesupersaturation degree “S” was 4.1 or less, alternatively, themassecuite had such suitable flowability that the purging could be donewithout any difficulty. Thus, it was found that the supersaturationdegree “S” on the basis of the temperature on the completion of thecrystallization was 4.1 or less under a condition for the industrialcrystal production of DFA III from a mother solution for thecrystallization at pH 5 or more. When the supersaturation degree “S” wasless than 1.3, the crystal yield was 20% or less. Accordingly, it wasfound that the supersaturation degree “S” was preferably 1.3 or more to4.1 or less, more preferably 1.5 or more to 4.1 or less and still morepreferably 2.3 or more to 4.1 or less, from the standpoint of thecrystal yield.

The term “solid concentration” referred to in accordance with theinvention is the ratio of solid in a solution (in w/w %), as determinedon the basis of the weight of the solid remaining after water in thesolution is removed by drying method. For the practical control of theproduction process, the value of R-Bx (Refractometric Brix Degree) canalso be used in a simple manner.

Based on these useful new findings, the invention has been achievedfinally, as a consequence of further research works and examinations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a flow chart of the production of thecrystals of DFA III, comprising the purification and crystallizationstep of a solution containing DFA III.

FIG. 2 shows an example of a flow chart of the purification bychromatography.

FIG. 3 shows the composition of a mother solution at a step for crudecrystallization as well as the crystal yield thereof, whereindividually, -▪- represents the purity of DFA III in dry substance (%);-- represents the crystal yield (%) of DFA III; -□- represents thepurity of fructooligosaccharide in dry substance (%); -⋄- represents thepurity of sucrose in dry substance (%); -Δ- represents the purity offructose in dry substance (%); and -◯- represents pH. Hereinbelow, thesymbols in FIGS. 4, 5 and 6 represent the same meanings as describedabove.

FIG. 4 represents the composition of a mother solution at the step ofthe crystallization as well as the crystal yield.

FIG. 5 represents the composition of a mother solution at the step ofthe crude crystallization as well as the crystal yield, when the pHduring the purification and crystallization step was maintained at 5 ormore via the addition of caustic soda.

FIG. 6 represents the composition of a mother solution at the step ofthe crystallization as well as the crystal yield, when the pH during thepurification and crystallization step was maintained at 5 or more viathe addition of caustic soda.

FIG. 7 shows the change of the DFA III crystal yield in case thatsucrose- and fructose solutions were added to the DFA III solution.

FIG. 8 shows the influence (1) of fructooligosaccharide, sucrose andfructose contained in a DFA III-containing solution on the DFA IIIcrystal yield. In the figure, individually, FOS representsfructooligosaccharide; Suc represents sucrose; Fru represents fructose;Blank represents control.

FIG. 9 shows the influence (2) of the contents of sucrose (Suc),fructose (Fru), and sucrose in combination with fructose (Suc+Fru) in aDFA III-containing solution on the DFA III crystal yield.

FIG. 10 shows the influence of organic acid salts (Na acetate+Naformate) contained in a DFA III-containing solution on the DFA IIIcrystal yield.

FIG. 11 shows the influence (1) of the pH of a DFA III-containingsolution on the DFA III crystal yield.

FIG. 12 shows the influence (2) of the pH of a DFA III-containingsolution on the DFA III crystal yield.

FIG. 13 shows the influence (1) of the pH of a mother solution for thecrude crystallization on the DFA III crystal yield.

FIG. 14 shows the solubility of DFA III and an approximate curve of thesolubility. In the figure, the symbol “◯” expresses the solubility ofDFA III (observed value) while the symbol “−” expresses an approximatecurve of the DFA III solubility.

The invention is now described in detail hereinbelow.

The invention relates to an efficient industrial production of thecrystals of DFA III at a high purity without lowering the crystal yield,by purifying a liquid containing DFA III. With attention focused on thesignificance of the pH of the liquid containing DFA III, first, theinventors made investigations to find that the liquid should essentiallybe adjusted to pH 5 or more. Based on the useful new finding, theinventors made research works and examinations. Finally, the inventionhas been achieved.

In accordance with the invention, a liquid containing DFA III ispurified to produce the crystals of DFA III, where the liquid containingDFA III is at pH 5 or more.

Industrial crystallization of DFA III has never been done in the relatedart. Therefore, no examination has been done about the pH thereof or noattention has been focused on the pH thereof. The pH influence on theDFA III crystallization was first focused on by the present inventorsduring the course of research works about the industrial DFA IIIcrystallization as made by the inventors. Thus, it is an absolutely newfinding. In accordance with the invention, the problematic issue hasdrawn attention for the first time during the industrial research worksrelating to the DFA III crystallization. Thus, it can be recognized thatthe technical issue itself is new. Hence, reasonably, the means forsolving the problem is also novel.

The invention encompasses those described below.

1. A process for producing the crystals of difructose dianhydride III(DFA III), where a solution containing difructose dianhydride III (DFAIII) is at pH 5 or more.

2. A process for producing the crystals of DFA III as described above in1, where the pH of the solution containing DFA III is adjusted andmaintained with at least one of an alkali addition method, achromatographic method and an anion exchange resin method.

3. A process for producing the crystals of DFA III as described above in1 and 2, where the solution containing DFA III is a solution prepared byreacting inulin with fructosyltransferase, and defecating and filteringthe resulting solution.

4. A process for producing the crystals of DFA III as described above in3, where inulin is at a fructose polymerization degree of 10 to 60 andat a polysaccharide purity of 70% or more in dry substance.

5. A process for producing the crystals of DFA III as described above inany one of 1 through 4, comprising a step of defecating and filteringsolutions containing DFA III and concentrating the resulting filtratesfor crystallization (purification and crystallization step), which stepranges from crude DFA III solutions through crude crystallization tocrystallization as a product, where at least one of the solutionscontaining DFA III is at pH 5 or more.

6. A process for producing the crystals of DFA III as described above in5, where the purification and crystallization step is done in arecycling system.

7. A process for producing the crystals of DFA III as described above inany one of 1 through 6, where the supersaturation degree of a mothersolution for the crystallization or a mother solution for the crudecrystallization, which is on the basis of the solubility at thetemperature on the completion of the cooling and crystallization, is 1.3to 4.1.

8. A process for producing the crystals of DFA III, where the fructosecontent in dry substance in a DFA III-containing mother solution for thecrystallization or a DFA III-containing mother solution for the crudecrystallization is 5% or less.

9. A process for producing the crystals of DFA III as described above in8, where fructooligosaccharide and/or fructose is removed by using anyone of chromatographic treatment and yeast treatment as a method foradjusting the fructose content in dry substance to 5% or less.

10. The crystals of DFA III as produced by a process described above inany one of 1 through 9.

In accordance with the invention, the crystals of DFA III at a highpurity can efficiently be produced industrially by purifying solutionscontaining DFA III, where at least one, preferably all of the solutionscontaining DFA III are at pH or more.

So as to practice the invention, at least one or all of the solutionscontaining DFA III are adjusted to pH 5 or more for crystallizationduring the production steps of the crystals of DFA III (one examplethereof is shown in FIG. 1).

The process for producing the crystals of DFA III is described belowwith reference to FIG. 1 illustrating one example thereof.

Raw materials for solutions containing DFA III include solutions of DFAIII synthetically prepared by reacting inulin or an inulin-containingsolution with fructosyltransferase, and additionally include solutionsof DFA III prepared by chemical synthesis.

Inulin as one of the raw materials is a fructose polymer where numerousfructose molecules are connected in series to one glucose molecule.Enzymes working for generating DFA III broadly includingfructosyltransferase, preferably inulin fructotransferase (IFT) reactwith the raw material inulin.

Microorganisms generating IFT include those described below.

Non-limiting examples thereof are listed below.

Arthrobacter sp.; Arthrobacter ureafaciens IFO 12140; Arthrobacterglobiformis IFO 12137; Arthrobacter pascens IFO 12139; Bacillus sp.;Kluyveromyces marxianus var. marxianus: Streptomyces sp.; Enterobactersp.

In case of using enzymes derived from these microorganisms, then,separated and purified enzymes and crudely purified enzymes, microbialcultures, and treated products of microbial cultures (culturesupernatants, separated bacterial cells, disrupted bacterial cells,etc.) may also be used. In case that the crystal of DFA III is to beused for foods, fructosyltransferase, particularly IFT is preferablyused as such enzyme. In addition to the enzymes derived from thesemicroorganisms, Arthrobacter sp. strain AHU 1753 internationallydeposited lately as FERN BP-8296 at the International Patent OrganismDepositary, the National Institute of Advanced Industrial Science andTechnology has a great potency to generate IFT. Therefore, the enzymederived from the strain can be used preferably.

For example, reaction with a crude enzyme, a purified enzyme, or anenzyme-containing material of inulin fructotransferase (depolymerizing)(IFT) derived from above-mentioned Arthrobacter sp. strain AHU 1753(FERM BP-8296) at 5000 units of the enzyme/kgφinulin under agitation at60° C. for 24 hours allows hydration and transfer to generate anenzymatic reaction solution containing DFA III. By inactivating theenzyme, a solution of DFA III prepared enzymatically can be obtained. Asolution of DFA III prepared by chemical synthesis can be also obtained.

The thus obtained solution of DFA III prepared enzymatically or bychemical synthesis is defined, singly or in admixture with othersolutions containing DFA III, as a crude DFA III solution. The crude DFAIII solution is subsequently defecated and filtered. The defecation andfiltration step means a step for the treatment of the crude DFA IIIsolution with active charcoal and the treatment for separating solidsfrom liquids. The treatment with active charcoal is a treatmentcomprising adding a small amount of powdery active charcoal to the crudeDFA III solution to adsorb impurities except DFA III onto the activecharcoal, and if necessary to heat and/or agitate the resulting mixture.

As the powdery active charcoal, a powdery active charcoal of a meanparticle size of 15 to 50 microns, preferably 25 to 45 microns, morepreferably about 35 microns is used, which is at the maximum particlesize of 200 microns or less, preferably 170 microns or less, morepreferably 150 microns or less, for example 147 microns or less. Theamount of the powdery active charcoal to be added is 5% or less,preferably 0.1 to 3%, more preferably 0.5 to 1.5% of the solid contents,and may be adjusted appropriately, depending on the composition of thecrude DFA III solution.

For the treatment for separating solids from liquids, at least one offiltration with auxiliary filtration agents such as Hi-Flo Supercell(Wako Pure Chemical Ind.) and diatomaceous earth (for example,filtration with a ceramic filtration machine; Type PR-12 manufactured byJapan Pall K.K. may be used), filtration with a membrane filter (MF),the continuous centrifugation method, the molecular sieve method, thereverse osmosis method, and, in some cases, an ultrafiltration (UF)membrane are appropriately used. The separation of solids from liquidsmay be done at atmospheric pressure, under pressure or at reducedpressure.

Specifically, for example, Taiko Active Charcoal S (manufactured byFutamura Kagaku Kogyo K.K.; the mean particle size of about 35 micronsbut not more than 147 microns) is added at a ratio of 1% on a solidcontent basis to the inactivated IFT enzyme solution, for agitation at60° C. for 10 minutes. On completion, the solution is filtered throughdiatomaceous earth (Radiolite 700, manufactured by Showa Chemical Ind.).Specifically, the diatomaceous earth is pre-coated on the exteriorsurface of a ceramic cylinder (ceramic tube of Type PR-12 asmanufactured by Japan Pall K.K.), while a reaction solution containingactive charcoal is passed through the outside of the cylinder underpressure, and is then filtered under pressure, to recover the filtratefrom the inside of the cylinder.

The filtrate recovered via the defecation and filtration treatment ofthe DFA III-containing solution (crude solution) is concentrated by ageneral method. For example, the filtrate is concentrated in a calandriaevaporator for use in producing sugar and the like (for example, at 60to 80° C. and at 120 mmHg or less), to obtain a concentrate solution.The concentrate solution may satisfactorily be concentrated to a solidconcentration of 60 to 85%, for example about 77%.

In accordance with the invention, the crude DFA III solution obtainedfrom a solution of DFA III prepared enzymatically or a solution of DFAIII prepared by chemical synthesis is preferably retained at pH 5 ormore between the defecation and filtration step and the concentrationstep. By adding for example sodium hydroxide to the crude solution, thecrude solution may be adjusted to pH 5 or more.

A mother solution as the concentrate solution thus obtained, namely amother solution for the crude crystallization (at about 60° C.) istransferred into a crystallizer, to generate the crystals of DFA III ina cooling mode or a boiling system to obtain the crude crystals. In thiscase, the crystal of DFA III ground in a mortar and the like isdispersed in alcohol and the like, which is defined as a seed. The seed(seed crystals) is added at an appropriate amount to the mother solutionin appropriate timing to grow the crystals. The seeding method includesfull seeding method and shock seeding method. According to the fullseeding method, the amount of the seed is adjusted to 1% or more of theamount of DFA III in a mother solution for the crystallization or amother solution for the crude crystallization, to make a shift of theparticle distribution of the crystals of DFA III toward a smaller size.By the cooling crystallization method, the crystals of DFA III particlesare smaller at a lower seeding temperature by both the seeding methods.The temperature gradient during cooling and crystallization is adjustedinitially to a smaller level and subsequently to a larger level, whichmakes a smaller variation of the crystal particle size. As thecrystallizer, a crystallizer equipped with a circulating system and/oran agitation system is preferably used.

The mother solution for the crude crystallization so as to deposit thecrystals is separated with a centrifuge (3000 rpm, 1200 G) into a crudecrystals of DFA III and a crude crystal syrup.

The crude crystals of DFA III are again dissolved in lukewarm water, toprepare a purified DFA III solution, which is passed through adefecation and filtration step, then concentrated and crystallized bythe same method for the crude crystal, to obtain the product crystals.The resulting crystals are an octahedron odorless, colorless andtransparent in a neutral region, of which the melting point is 163.7° C.and the optical rotation [α]_(D) is 134.5.

In case that the pH of the solutions at the individual steps is adjustedand retained at 5 or more in accordance with the invention, the crudecrystal syrup and/or the crystal syrup separated in the aforementionedflow may be recycled to the crystal production system, if necessary.Using such recycling system, further, the recovery ratio of DFA III canbe improved. When a recycling system is established where the pH of thesolutions from the individual steps is never maintained or adjusted,substances inhibiting the crystallization of DFA III, such asmonosaccharide (fructose, in particular) and sucrose, significantlyincrease and accumulate in the solutions at the steps, while the pH ofthe mother solutions for the crystallization is greatly lowered, leadingto the decrease of the crystal yield during the DFA crystallization stepand additionally falling into a state such as no achievement of thecrystallization, most undesirably.

In accordance with the invention, it was found that the solutions fromthe individual steps were maintained or adjusted to pH 5 or more tosuppress the generation of monosaccharides, sucrose or acidic substances(such as organic acids) as factors inhibiting the crystallization of DFAIII. In addition to the method comprising adding alkaline agents, thechromatographic separation method and the yeast treatment of thesolutions containing the inhibitory substances from the steps enable theremoval of the inhibitory substances and the purification andcrystallization of DFA III. In other words, various products generatedduring all the steps for the purification and crystallization of DFA III(FIG. 1) were used in stock solutions for chromatography (at 40 to 75%of the solid concentration), to allow the purification andcrystallization for solutions containing DFA III. One example of thepurification flow chart by the chromatographic treatment is shown inFIG. 2.

The stock solution for chromatography (at a solid concentration of 40 to75%) is treated by chromatography, to separate a fraction of DFA III. Afraction enriched with DFA III at a purity similar to that of theredissolved solution described above (DFA III solution) is used as asolution for purifying DFA III, for defecation and filtration, or forconcentration and crystallization, to produce the product crystals(Route A). Otherwise, the enriched fraction is used as it is forcrystallization (Route B). Unlike the fraction enriched with DFA III, afraction not enriched with DFA III, which is at a low content of DFAIII, may satisfactorily be recycled to an appropriate position in theproduction flow chart (in the whole purification step ranging from theDFA III-containing solutions to the product DFA III, as shown in FIG. 1)(Route C). Further, a fraction not enriched with DFA III, containingfructooligosaccharide, monosaccharides such as fructose and acidicsubstances but containing only a small amount of DFA III, can be used asa raw material for feeds or may be disposed.

For the chromatographic separation method, the fixed bed mode (one-pathmode), the continuous mode (simulated moving bed mode) and thesemi-continuous mode (a combination of the fixed bed mode and thecontinuous mode) may be used. As the ion exchange resins to be packed insuch apparatuses, highly acidic ion exchange resins of for example Naform, K form and Ca form for use in chromatography can be used. Theresins are for example styrene-divinylbenzene-series resins of a uniformparticle size. Various chromatographic resins are commercially availablefrom manufacturers of ion exchange resins. Any such chromatographicresins applicable to sugar solutions may be used satisfactorily. Incasethat the purity of DFA III is low in a mother solution for thecrystallization, the chromatographic treatment is appropriately used soas to raise the purity.

The yeast treatment may satisfactorily be done by putting the DFAIII-containing solution in contact with yeast. Both the solution andyeast may be mixed together and incubated under agitation if necessaryor may be cultured in air purging. As the yeast, there may be usedappropriately baker's yeast, Japanese sake yeast, beer yeast, wine yeastand other various types of yeast. Additionally, dry yeast, squeezedyeast and other various commercially available yeast products may alsobe used. Because yeast decomposes or allows the incorporation offructooligosaccharide, sucrose and monosaccharides into bacterial cells,the yeast treatment is useful mainly for removing fructooligosaccharide,sucrose and/or monosaccharides outside the system.

In accordance with the invention, DFA III-containing solutions (mothersolutions for the crystallization) at less than 60% of the purity of DFAIII may industrially be crystallized.

So as to raise the purification level of the DFA III-containingsolutions at less than 60% of the purity of DFA III, in accordance withthe invention, the DFA III-containing solutions are treated by at leastone of the yeast treatment, the defecation and filtration treatment andthe chromatographic treatment, to highly raise the purity of DFA III inthe DFA III-containing solutions.

The main terms in accordance with the invention are now described belowwith reference to the production flow chart of the crystals of DFA IIIas shown in FIG. 1.

(Inulin)

The term “inulin” means plant-derived- or enzymatically synthesizedproduct-derived inulin or inulin-containing liquids, including forexample plant extracts from for example Jerusalem artichoke, burdock orchicory, solutions containing synthetic inulin prepared by the reactionof sucrose with an inulin synthase, or solutions resulting from thedefecation and filtration of such solutions, and additionally includinginulin-containing powders resulting from drying up the individualsolutions or crystallizing DFA III therein.

Using inulin as one of raw materials for solutions containing DFA III,which is at a fructose polymerization degree of 10 to 60 and at apolysaccharide purity of 70% or more, preferably 80% or more on a solidcontent basis, DFA III is efficiently generated. Using then the DFAIII-containing solution, the crystals of DFA III are producedefficiently.

(Solutions of DFA III Prepared Enzymatically or by Chemical Synthesis)

Solutions of DFA III prepared enzymatically or by chemical synthesisinclude solutions prepared by reacting inulin with the enzyme togenerate a solution containing DFA III and inactivating the enzyme ifnecessary and solutions of DFA III prepared by chemical synthesis.

(Crude DFA III Solution)

The term “crude DFA III solution” means the solutions of DFA IIIprepared enzymatically or by chemical synthesis themselves, andsolutions comprising at least one or more of crude crystal syrup,crystal syrup, chromatographically separated solutions, and fractions ofDFA III, as prepared by separating mother solutions into solids andliquids after crystallization at crystallization steps (for crudecrystallization, and crystallization). Additionally, the term also meansa solution prepared by mixing the solution of DFA III preparedenzymatically or by chemical synthesis with at least one of such crudecrystal syrup, crystal syrup, chromatographically separated solutionsand fractions of DFA III as obtained by chromatographic separation.

(Mother Solution for Crude Crystallization)

The term “mother solution for crude crystallization” is a dilutesolution prepared by a defecation treatment of the crude DFA IIIsolution with active charcoal or with ion exchange resins or bychromatography or with yeast, if necessary and subjecting the resultingproduct to solid/liquid separation such as filtration (namely,defecation and filtration). Additionally, the term also means aconcentrate of the crude DFA III solution concentrated properly in aconcentration apparatus such as efficient can.

(Purified DFA III Solution)

The term “purified DFA III solution” means a solution comprising atleast one of a solution prepared by dissolving the crude crystals fromcrude crystallization in water (lukewarm water) to an appropriateconcentration or a fraction of DFA III as obtained by chromatographicseparation.

(Mother Solution for Crystallization)

The term “mother solution for crystallization” means a dilute solutionprepared by a defecation treatment of the purified DFA III solution withactive charcoal or ion exchange resins, or with yeast, if necessary andsubsequently subjecting the resulting product to solid/liquid separationsuch as filtration (namely, defecation and filtration). Additionally,the term also means a concentrate prepared by concentrating at least oneof the purified DFA III solution, the crystal syrup, and fractions withDFA III concentrated properly in a concentration apparatus such aseffect evaporator.

As described above, the mother solution containing DFA III for crudecrystallization and the mother solution containing the same forcrystallization are solutions containing DFA III, which are suppliedexclusively into crystallizer of cooling mode and/or boiling mode so asto crystallize DFA III.

(Purification and Crystallization Step of DFA III)

The term “purification and crystallization step of DFA III” means a stepfor defecating and filtering all solutions containing DFA III andsubsequently concentrating the filtrates for crystallization, which stepranges from the crude DFA III solutions through crude crystallization tocrystallization as a product.

(Solutions Containing DFA III)

The term “solutions containing DFA III” means all solutions containingDFA III as generated in the production flow of the crystals of DFA III,including for example at least one of crude DFA III solutions, mothersolutions for the crude crystallization, mother solutions for thecrystallization, crude crystal syrup, crystal syrup, purified DFA IIIsolutions, chromatographically separated solutions, and fractions of DFAIII as obtained by chromatographic separation (chromatographic fractionsof DFA III).

So as to practice the invention, the solutions containing DFA III shouldbe adjusted to pH 5 or more. When the crystallization of DFA III is inprogress, the pH decreases to lower the crystal yield, as first found bythe inventors. The pH may satisfactorily be 5 or more, preferably 5 to8, more preferably 6 to 8. A higher pH level is also possible, but theadjustment of the pH requires a larger amount of alkalis such as causticsoda and caustic potassium, uselessly and costly, additionally causingsafety problems during labor works.

As to the solutions containing DFA III, at least one and preferably allof those defined above are essentially at pH 5 or more. The pH thereofin a transfer pipe in the production process of the crystals of DFA IIIincluding the purification and crystallization step of DFA III ispreferably at 5 or more.

As described above, in accordance with the invention, the solutionscontaining DFA III are essentially at pH 5 or more so as to raise thecrystal yield of DFA III. As a consequence of additional research works,unexpectedly, the inventors first found that the presence of sucrose andfructose lowered the crystal yield of DFA III and that the crystal yieldof DFA III could be raised when a mother solution for thecrystallization contained fructose at 5% or less, preferably 1% or lesson a solid content basis. Then, the inventors first verified that suchsugar suppression could be attained by adjusting the solution to pH 5 ormore. When the solutions containing DFA III are at pH 5 or more and themother solutions for the crude crystallization and the mother solutionsfor the crystallization are at a fructose content of 5% or less on asolid content basis and additionally when these conditions areconcurrently satisfied, it is found that the maximum crystallization ofDFA III can synergistically be raised.

Advantages of the Invention

DFA III can be crystallized and produced industrially efficiently whenthe solutions containing DFA III are at pH 5 or more and fructosecontent in the mother solutions for the crude crystallization and themother solutions for the crystallization are at 5% or less on a solidcontent basis.

The invention is now described in detail in the following Examples butthe invention is not limited to these Examples.

EXAMPLE 1

Using a test plant and according to a part of the flow chart shown inFIG. 1, the production of the crystals of DFA III in a recycling modewas tested.

As the levels of sugars in solutions containing DFA III as used at thetest, further, the values from the composition analysis by HPLC wereused.

(1) Enzymatic Reaction Step

An enzyme solution from the culture of Arthrobacter sp. strain AHU 1753(the enzyme titer of about 500,000 U) was added to a solution of 100 kgof commercially available inulin as a daily processable amount (ORAFTI;the product name of RAFTILINE HP), for reaction at 60° C. for 12 hours,to obtain a solution of DFA III prepared enzymatically.

(2) Discoloring and Defecating Step

As a discoloring treatment, active charcoal (Futamura Kagaku Kogyo K.K.;Taiko Active Charcoal KW50) was added at a ratio of 0.5% on a solidcontent basis to the solution of DFA III enzymatically preparedsynthetically, for incubation at 80° C. for 30 minutes, followed byfiltration through diatomaceous earth.

(3) Crude Crystallization Step

The discolored solution of DFA III prepared enzymatically wasconcentrated to 76% as the solid concentration, which was used as amother solution for crude crystallization. Then, the seed crystals(seed) were added to the mother solution at 50° C., followed by coolingthe resulting mother solution over 12 hours to 10° C. to generate thecrude crystals of DFA III. The mother solution of the crude crystals(also referred to as crude crystal massecuite) was centrifuged andseparated into the crude crystals and a crude crystal syrup.

(4) Purification and Crystallization Step

The crude crystals were again dissolved and then the thus-obtainedsolution was concentrated to 75% as the solid concentration, which wasthen used as a mother solution for crystallization. Then, the seedcrystals were added to the mother solution at 50° C., and the resultingmother solution was cooled over 12 hours to 10° C. to generate thecrystals. The crystal massecuite was centrifuged and separated into thecrystals and a crystal syrup.

(5) Recycling Step

So as to elevate the recovery ratio of DFA III, 50% of the crude crystalsyrup was mixed with the solution after the termination of the enzymaticreaction, while the remaining crude crystal syrup was used as a rawmaterial for feeds. Additionally, 50% of the crystal syrup was back tothe evaporator at the crude crystallization step, while the remaining50% was back to the evaporator at the crystallization step.

(6) Calculation of Crystal Yield

The crystal yields of the crude crystals and the crystals werecalculated by the following formula in this Example.

Crystal yield (%)=(P/Q)×100

In the formula, the individual symbols or alphabets express thefollowing meanings.

P: M−N

Q: (100−N)M/100

M: DFA III purity in mother solution for (crude) crystallization

N: DFA III purity in (crude) crystal syrup.

(7) Production Test

According to the steps described above in (1) to (5), production wasstarted. On day 4 from the test start, the step for crudecrystallization was initiated, while the step for crystallization wasstarted on day 7 from the test start. The step for crude crystallizationis schematically shown (the composition of the mother solution and thecrystal yield) in FIG. 3. The crude crystal yield started to decrease onday 10 from the test start and decreased to 30% or less on day 13.Therefore, the ratio of the crude crystal syrup to be recycled wasreduced from 50% to 30%. Nonetheless, the crystal yield was subsequentlylowered continuously. On day 17, the crystal yield was below 10%. TheDFA III purity in the mother solution for crude crystallization was alittle less than 80% throughout the test period, with no largervariation. Concerning the composition of impurities, meanwhile,fructooligosaccharide was decreased over time during the test, whilefructose believed as a decomposition product thereof was increased. Themother solution for crude crystallization was at pH 5.1 at the teststart and was gradually decreased to around 4. The purification andcrystallization step is schematically shown in FIG. 4. No largevariation in the sugar composition during the period was observed, whilethe crystal yield was gradually lowered during the test period. Themother solution for crystallization was at pH 4.8 at the start and wasgradually decreased to around 4.

EXAMPLE 2

Example 1 apparently indicated that the crystal yield of DFA III wasgradually lowered when DFA III was produced in the recycling mode.Because the mother solution of crystallization was at a decreased pH,which was accompanied by the progress of the decomposition offructooligosaccharide, then, some relation between the decrease of thecrystal yield and the decomposition progress was suggested. At theproduction test in this Example, caustic soda was added to the mothersolution for crude crystallization (the solution before concentration)and a solution of the crude crystals redissolved, after the terminationof the enzymatic reaction, to prevent the pH decrease of the solutionsat the individual steps. Except for the procedure, the production wasdone by the same method as in Example 1.

The step for crude crystallization and the step for crystallization areschematically shown in FIGS. 5 and 6. Via the addition of caustic soda,the individual mother solutions for such crystallization changed withina range of 5.1 to 5.6 and a range of 5.4 to 5.7, respectively, while thedecomposition of fructooligosaccharide was suppressed. Additionally, theindividual crystal yields could be retained at high levels.

EXAMPLE 3

Compared with other sugars, DFA III itself is a substance highlyresistant against heat and acids. When the solutions at the productionsteps are at lower pHs in the industrial steps for producing DFA III asshown in FIG. 1, impurities are decomposed to generate other substancesexcept DFA III. Additionally because solutions containing DFA III foruse in the crystallization are recycled and used, it is indicated thatthe pH thereof is increasingly reduced while other substances except DFAIII also accumulate. In the test production in Example 1, actually, thepH of the solutions at the steps is gradually decreased, causing thedecrease of the ratio of fructooligosaccharide, so that fructoseaccumulates.

The inventors therefore carried out a table test so as to determine howthe sugar composition of the solution after the termination of theenzymatic reaction as prepared in Example 1 was modified underconditions of pH (3 to 7) and temperature (70° C., 80° C.) Consequently,almost no modification of the composition of the contained sugars wasobserved in 24 hours under conditions of 70° C. and pH 5 or more. At pH4, the decomposition of sugars such as tetrasaccharides and largersaccharides and the increase of fructose were observed in 8 hours. At pH3, the tendency was further enhanced. The modification of the sugarcomposition as observed under individual pH conditions at 70° C. wasfurther accelerated when the temperature was at 80° C. At 80° C., almostno modification thereof was observed in 12 hours even at pH of 5 ormore, in the same manner as observed at 70° C. At the time 24 hourslater, however, the decomposition of sugars such as tetrasaccharides andlarger saccharides and the increase of fructose were likely observed.

The inventors further examined acidic substances in the mother solutionfor the crude crystallization in Example 1, which was at a decreased pHof 4. It was found that the mother solution contained organic acids(lactic acid, acetic acid, formic acid, etc.) at a concentration of 30to 40 mg/100 g•sample. At a table test, the inventors found that in theresulting aqueous fructose solution when left to stand alone inenvironment at 80° C. for a long time, organic acids increasedgradually, involving the decrease of the pH.

Based on the results of the analytical values in Examples 1 through 3,the inventors carried out table tests in Examples 4 through 7, so as tofind how highly variable fructooligosaccharide, organic acid, fructose,sucrose and pH affected the crystal yield. Herein, the crystal yield wascalculated according to the following formula, which was used inExamples 4 to 7.

Crystal yield (%)=A/B×100

In the formula, the individual symbols and alphabets represent thosedescribed below.

A: the weight (in gram) of the crystals of DFA III obtained viacrystallization

B: the content (in gram) of DFA III in a mother solution forcrystallization

EXAMPLE 4 Crystal Yield when a Sucrose Solution or a Fructose Solutionwas Added to an Aqueous Solution of DFA III at a Purity of 99.9%)

A sucrose solution at a solid concentration of 71% or a fructosesolution at a solid concentration of 71% was added at 3 g, 15 g, and 30g (1.0, 4.8 and 9.1%, respectively as the amount of sucrose (fructose)on a solid content basis) to 300 g of a DFA III solution adjusted to asolid concentration of 71%, for crystallization. A control with noaddition of such sucrose solution or fructose solution was also used forcrystallization. At a test where the sucrose (fructose) solution wasadded at 30 g, the seed crystals were dissolved thoroughly duringseeding at 50° C. Therefore, seeding was again done at 45° C. Then, thesolutions were cooled to 10° C. to grow the crystals. The test resultsare shown in FIG. 7. By using mother solutions for crystallization at aconstant solid concentration and at a constant DFA III amount whileincreasing the amounts of sucrose and fructose to be added, the amountof the crystals generated was measured. Following the increase of theamounts added, the amount of the crystals of DFA III generated wasdecreased in both cases.

EXAMPLE 5 Influence of Impurities Contaminated in DFA III-ContainingSolution on Crystal Generation

(1) A test was done by using mother solutions at a constant solidconcentration and a constant DFA III amount. Consequently, the amount ofthe generated crystals of DFA III was decreased, following the increaseof the amounts of sucrose and fructose added. Because it was suggestedthat the results might potentially be ascribed to the reduction of thepurity of DFA III, the influence of the difference in contaminatedimpurities on the crystal generation was tested.

A fructooligosaccharide (MEIOLIGO P manufactured by Meiji Seika Kaisha,Ltd.: a mixture of tetrasaccharides, trisaccharides, disaccharides, andfructose at the contents of 65.2%, 32.8%, 1.2%, and 0.8%, respectivelyon a solid content basis) solution at a solid concentration of 71%, asucrose solution and a fructose solution both at a solid concentrationof 71% were individually added at 30 g (9.1% on a solid content basis)to 300 g of a DFA III solution adjusted to a solid concentration of 71%,for crystallization. A control with no addition of such solutions wasalso used for crystallization. The seeding temperature was 45° C. Thesolutions were cooled to 10° C. to grow the crystals. The test resultsare shown in FIG. 8.

FIG. 8 shows the results that in the case of replacingfructooligosaccharide with sucrose or fructose compared with thepresence of fructooligosaccharide alone as impurities, the amount of thecrystals of DFA III generated was less and that the crystallization ofDFA III was suppressed even at the same DFA III purity whenfructooligosaccharide was decomposed to generate sucrose and fructose.Such results were verified.

(2) Influence of Composition of Impurities Contaminated in DFA III onCrystal Generation

Then, the influence of the presence of sucrose or fructose alone or thepresence of both sucrose and fructose was examined.

A sucrose solution at a solid concentration of 71%, and a fructosesolution at a solid concentration of 71%, were individually added at 30g (9.1% on a solid content basis) to 300 g of a DFA III solutionadjusted to a solid concentration of 71%, for crystallization. Acombination of the sucrose solution at 15 g and the fructose solution at15 g was also added to 300 g of the DFA III solution (the total ofsucrose and fructose corresponds to 9.1% on a solid content basis). Acontrol with no addition of such sucrose solution or fructose solutionor the combination was also used for crystallization. The seedingtemperature was 45° C. The solutions were cooled to 10° C. to grow thecrystals. The test results are shown in FIG. 9.

FIG. 9 shows the results that the single addition of sucrose or fructosewas more highly inhibitory than the addition of sucrose and fructoseindividually at half of their amounts described above, even at the samepurity of DFA III. Therefore, it was suggested that the DFA IIIcrystallization might be influenced by a higher content of eithersucrose or fructose existing as impurities. However, the amount ofsucrose generated never exceeds the amount of fructose generated, onsite in producing the crystals. Hence, it is indicated that the amountof the crystals generated may be influenced by the amount of fructose.

Compared with the presence of fructooligosaccharide alone as impurities,it was indicated that the presence of sucrose and fructose generated asmaller amount of the crystals of DFA III, where the level of thegeneration was influenced by either one of sucrose and fructose, whichis at a higher content. At the same level of impurities, nonetheless,the amount of the crystal generated was larger than in the control, whensucrose crystals or fructose crystals in solids were added to the DFAIII solution. Thus, it was indicated that the DFA III crystals could berecovered even in the presence of sucrose and fructose, at a yieldsimilar to the case in the absence of both sucrose and fructose, byraising appropriately the concentration of the mother solution.

(3) Influence of the Composition of Impurities Contaminated in DFA IIISolution on Crystal Generation

Then, it was examined the influence of organic acids of which thepresence was confirmed by the analysis of the solutions at the steps.The organic acids of which the presence was confirmed in the solutionsat the steps were lactic acid, acetic acid, formic acid and other acids(with plural peaks unidentified). Herein, acetic acid and formic acidgenerated during the thermal decomposition of fructose were tested.Because the analytical results of the solutions at the steps indicatethat the contents of the individual organic acids detected in theconcentrate solution from the defecated and filtered solution of thecrude DFA III solution were about 30 to 40 mg/100 g•sample, the amountsof individual salts of the organic acids to be added were adjusted to 0to 100 mg/100 g•DFA III solution.

A mix solution of sodium acetate and sodium formate was added to giverespective contents of 10 mg of sodium acetate and 10 mg of sodiumformate, 50 mg of sodium acetate and 50 mg of sodium formate, and 100 mgof sodium acetate and 100 mg of sodium formate per 100 g•DFA IIIsolution, to 300 g of the DFA III solution adjusted to a solidconcentration of 71%, to which pure water was added so as to adjust thesolid concentration (to the final solid concentration of 70.3%), forcrystallization. A control with no addition of any such mix solution wasalso adjusted to the same solid concentration, by adding pure water. Theseeding temperature was 50° C. The solutions were cooled to 10° C. togrow the crystals. The test results are shown in FIG. 10.

FIG. 10 indicates that the organic acid salts never inhibited thecrystallization of DFA III despite some variation of the amount of thecrystals generated. Further, the crystal generation in the control andin the DFA III solution, to which sodium acetate and sodium formate wereindividually added at 10 mg/100 g, proceeded slowly, immediately afterthe seeding, because these solutions were at lower solid concentration,namely 70.3% which was slightly lower concentration than the conditionsof the past tests. Compared with these results, the crystal generationin the DFA III solutions to which sodium acetate and sodium formate wereindividually added at 50 mg/100 g and at 100 mg/100 g proceeded faster,immediately after the seeding. It was examined what caused thediscrepancy. It was indicated that since the mix solution of sodiumacetate and sodium formate was at such a high pH of 8.6, the mothersolution after the mixture solution was added was around pH 7 in thelatter case. Therefore, the inventors considered that the change of thepH of the solutions at the steps due to the generation of organic acidsat the production steps might have some influence on the generation ofthe crystals of DFA III.

EXAMPLE 6 Influence of pH on the DFA III crystallization

(1) So as to verify the influence of the pH of the mother solution foruse in crystallization on the generation of the crystals of DFA III, thechange of the generated crystal amount was examined at variable pHs inthe presence of organic acid salts (sodium acetate and sodium formate).

A solution of sodium acetate and sodium formate was added at 100 mgsodium acetate and 100 mg sodium formate per 100 g•DFA III solution to300 g of the DFA III solution adjusted to a solid concentration of 73%.The resulting solution was adjusted to pH 7, 5, 4 and 3, with 5Nhydrochloric acid, and adjusted to a solid concentration of 71% withpure water, for crystallization. The seeding temperature was 50° C. Thesolution were cooled to 25° C. to grow the crystals. The test resultsare shown in FIG. 11.

FIG. 11 shows the results that the amount of the crystals generated wasinfluenced by the pH and that the amount thereof was the largest at thepH 7, was the smallest at the pH 4, and was the same level at pH 3 andthe amount at pH 5.

(2) So as to examine whether or not the phenomenon depended singly on pHand occurred even without any presence of organic acid salts, the DFAIII solution was pH adjusted with hydrochloric acid and caustic soda, totest the change of the amount of the crystals generated. 300 g of theDFA III solution adjusted to a solid concentration of 71.5% was adjustedto pH 7, 5, 4 and 3 with 1N hydrochloric acid and 1N caustic soda, towhich pure water was subsequently added to adjust the solidconcentration of 71%, for crystallization. The seeding temperature was50° C. The solutions were cooled to 25° C. to grow the crystals. Thetest results are shown in FIG. 12.

The test results are more or less different from the results in thepresence of organic acid salts, in that the amount of the crystalsgenerated at pH 5 was less. However, the same results were obtained inthat at pH 7, the amount of the crystals generated was the largest, withthe amount was at minimum at pH 4. So as to verify that the results werenever attributed to the difference in the concentration of inorganicacids, further, the pH adjustment was done in the same manner in thepresence of 1% sodium chloride, for crystallization. The results weresimilar to those when the crystallization was done after the pHadjustment in the presence of organic acid salts. This indicates thatthe presence of salts reduces the crystallization inhibitory action atpH 5.

(3) Those described below were verified using the crude crystal mothersolution at a practical step.

After the crystals deposited in a crude crystal mother solutioncollected (at a DFA III purity of 75.9%) were completely dissolved, theresulting solution was concentrated to about 76% as a solidconcentration, which was adjusted to pH 7, 5, 4 and 3 with 5Nhydrochloric acid or 5N caustic soda. Pure water was added to adjust thesolid concentration to 75 (or 73) %, for crystallization. The solutionwere cooled to 25° C. to grow the crystals, which were at a solidconcentration of 75%, while the solutions were cooled to 10° C., whichwere at a solid concentration of 73%. The seeding temperature was 50° C.(at a solid concentration of 75%) or 45° C. (at a solid concentration of73%). The test results are shown in FIG. 13. At any of the solidconcentrations, the crystal yield of DFA III was the smallest at pH 4.

EXAMPLE 7 Influence of the pH of the Mother Solution for (Crude)Crystallization and Supersaturation Degree on DFA III

So as to determine the optimal concentration level of the mothersolution for crystallizing DFA III vs. the pH change as a factorinhibiting the DFA III crystallization, examination was done.

As shown in FIG. 14, beforehand, the solubility of DFA III (saturatedsolid concentration %) at respective temperature was examined. Based onthe measured levels, an approximate curve of the solubility was firstformulated and calculated as represented by the following formula(correlation coefficient R²=0.999).

Solubility (saturated solid concentration %)“Z”=−0.00058X ²+0.39X+48.8

Herein, X represents temperature (° C.).

Then, the supersaturation degree “S” of the mother solution for the DFAIII crystallization at a purity “P” to the DFA III solubility at thetemperature “X”° C. on completion of cooling crystallization was definedby the following formula. The supersaturation degree “S” was theconcentration level required for the crystallization of the mothersolution for the DFA III crystallization, as expressed in numericalfigure.

Supersaturation degree“S”=[Y×P/(100−Y)]/[Z/(100−Z)×100]

Herein, Y: the solid concentration of the mother solution for the DFAIII crystallization (%);P: the purity of DFA III in the mother solution for the DFA IIIcrystallization (%); andZ: solubility (X: the temperature on completion of coolingcrystallization (° C.)).

Using subsequently the DFA III solutions at practical steps, theinfluence of the supersaturation degree “S” defined above on the DFA IIIcrystallization was examined at a table test under variable pHs of themother solutions for crystallization, as factors inhibiting thecrystallization. The pH adjustment was done by adding 5N HCl or 5N NaOHto the DFA III solutions from the steps. After the solutions wereconcentrated to various concentrations, the resulting individualsolutions were used as mother solutions for the crystallization, forseeding at 50° C. and cooling down to 10° C. for growing the crystals.According to the formula, the supersaturation degree “S” was calculatedat the temperature 10° C. on the completion of cooling crystallization.

The results about the examination of the relation between the pH of themother solutions for the crystallization and the supersaturation degree“S” are shown in Table 1. When the mother solutions for thecrystallization were at pH 5 to 7, the massecuite flowability wassignificantly reduced in the mother solutions containing DFA III at anypurity for the crystallization, under conditions that thesupersaturation degree “S” was 4.4 or more. Thus, apparently, purgingwas tough. Under conditions that the supersaturation degree “S” was 4.1or less, meanwhile, the massecuite was at such appropriate flowabilitythat the purging could be done without any difficulty. It was indicatedthat the supersaturation degree “S” on the basis of the temperature onthe completion of the crystallization was 4.1 or less under industrialconditions for producing the crystals of DFA III where the mothersolutions for the crystallization were at pH 5 or more. When thesupersaturation degree “S” was less than 1.3, the crystal yield was 20%or less. From the standpoint of the crystal yield, it was indicated thatthe supersaturation degree “S” was preferably 1.3 or more to 4.1 orless, more preferably 1.5 or more to 4.1 or less, still more preferably2.3 or more to 4.1 or less.

TABLE 1 Influences of the pHs of the various DFA III-containingsolutions and the supersaturation degree “S” on the crystal yieldSupersaturation pH of mother solution for crystallization degree “S” 5 67 Crystal yield (%) of DFA III-containing solution “A” by coolingcrystallization 1.3 21.0 21.6 21.9 1.5 29.4 31.0 31.4 1.6 36.0 36.8 37.02.3 53.1 55.3 56.1 4.1 67.1 68.5 68.8 4.7 x x x Crystal yield (%) of DFAIII-containing solution “B” by cooling crystallization 1.3 20.6 21.121.3 1.5 31.2 32.4 32.6 1.6 36.1 36.8 38.1 2.3 53.3 54.2 54.7 4.1 65.065.1 65.4 4.7 x x x Composition of solid contents in the solution “A”:DFA III at 99.5%, ashes at 0.1% and fructooligosaccharide at 0.4%.

Composition of solid contents in the solution “B”: DFA III at 79.7%,ashes at 0.3%, fructooligosaccharide at 18.3%, sucrose at 0.2% andfructose at 1.0%.

In the table, the symbol “×” represents that purging was tough due tothe decrease of the massecuite flowability.

Accession No.: FERM BP-8296

Bacterial strain deposited: Arthrobacter sp. AHU 1753

Name of Depositary: The International Patent Organism Depositary, TheNational Institute of Advanced Industrial Science and Technology (AIST)

Address of Depositary: AIST Tsukuba Central 6, 1-1, Higashi 1-chome,Tsukuba-shi, Ibaraki-ken, 305-8566, Japan (zip code: 305-8566)Deposition Date: Feb. 18, 2003

1-10. (canceled)
 11. A process for producing the crystals of difructosedianhydride III (DFA III), comprising: defecating and filtering asolution containing DFA III to obtain a filtrate; and concentrating thefiltrate to induce crystallization of the DFA III, wherein the solutionand the filtrate are maintained at a pH of 5 or higher.
 12. The processof claim 11, wherein the solution containing DFA III is a solutionprepared by reacting inulin with fructosyltransferase in a solution anddefecating and filtering the solution.
 13. The process of claim 12,wherein the inulin has fructose polymerization degree of 10 to 60 andhas a polysaccharide purity of 70% or more in a dry state.
 14. Theprocess of claim 11, wherein (1) the fructose content of the filtrate is5% or less on a solid content weight basis and (2) the supersaturationdegree of filtrate is 1.3 to 4.1.
 15. The process of claim 12, wherein(1) the fructose content of the filtrate is 5% or less on a solidcontent weight basis and (2) the supersaturation degree of the filtrateis 1.3 to 4.1.
 16. The process of claim 14, further comprising adjustingthe fructose content to 5% or less on a solid content weight basis byremoving fructooligosaccharide and/or fructose by chromatography methodand/or yeast treatment.
 17. The process of claim 15, further comprisingadjusting the fructose content to 5% or less on a solid content weightbasis by removing fructooligosaccharide and/or fructose bychromatography method and/or yeast treatment.
 18. The process of claim11, wherein the solution and the filtrate are maintained at a pH of 5 to8.
 19. The process of claim 11, wherein the solution and the filtrateare maintained at a pH of 6 to
 8. 20. The process of claim 11, whereinthe concentrated filtrate has a solid content of 60 to 85%.
 21. Theprocess of claim 11, wherein the DFA III crystals have a melting pointof 163.7° C. and an optical rotation of 134.5.
 22. The process of claim11, further comprising separating the crystals of DFA III from a crystalsyrup and recycling the crystal syrup to the defecating and filteringstep.